ArrayList.LastIndexOf Method (Object, Int32, Int32)

Searches for the specified Object and returns the zero-based index of the last occurrence within the range of elements in the ArrayList that contains the specified number of elements and ends at the specified index.

Starting with the .NET Framework 2.0, this method uses the collection’s objects’ Equals and CompareTo methods on item to determine whether item exists. In the earlier versions of the .NET Framework, this determination was made by using the Equals and CompareTo methods of the item parameter on the objects in the collection.

The following code example shows how to determine the index of the last occurrence of a specified element. Note that LastIndexOf is a backward search; therefore, count must be less than or equal to startIndex + 1.

import System.*;
import System.Collections.*;
public class SamplesArrayList
{
public static void main(String[] args)
{
// Creates and initializes a new ArrayList with three elements of the
// same value.
ArrayList myAL = new ArrayList();
myAL.Add("the");
myAL.Add("quick");
myAL.Add("brown");
myAL.Add("fox");
myAL.Add("jumps");
myAL.Add("over");
myAL.Add("the");
myAL.Add("lazy");
myAL.Add("dog");
myAL.Add("in");
myAL.Add("the");
myAL.Add("barn");
// Displays the values of the ArrayList.
Console.WriteLine("The ArrayList contains the following values:");
PrintIndexAndValues(myAL);
// Searches for the last occurrence of the duplicated value.
String myString = "the";
int myIndex = myAL.LastIndexOf(myString);
Console.WriteLine("The last occurrence of \"{0}\" is at index {1}.",
myString,(Int32)myIndex);
// Searches for the last occurrence of the duplicated value in the
// first section of the ArrayList.
myIndex = myAL.LastIndexOf(myString, 8);
Console.WriteLine("The last occurrence of \"{0}\" between the start"
+ " and index 8 is at index {1}.", myString, (Int32)myIndex);
// Searches for the last occurrence of the duplicated value in a
// section of the ArrayList. Note that the start index is greater
// than the end index because the search is done backward.
myIndex = myAL.LastIndexOf(myString, 10, 6);
Console.WriteLine("The last occurrence of \"{0}\" between index 10"
+ " and index 5 is at index {1}.", myString, (Int32)myIndex);
} //main
public static void PrintIndexAndValues(IEnumerable myList)
{
int i = 0;
IEnumerator objMyEnum = myList.GetEnumerator();
while (objMyEnum.MoveNext()) {
Object obj = objMyEnum.get_Current();
Console.WriteLine(" [{0}]: {1}", (Int32)i++, obj);
}
Console.WriteLine();
} //PrintIndexAndValues
} //SamplesArrayList
/*
This code produces the following output.
The ArrayList contains the following values:
[0]: the
[1]: quick
[2]: brown
[3]: fox
[4]: jumps
[5]: over
[6]: the
[7]: lazy
[8]: dog
[9]: in
[10]: the
[11]: barn
The last occurrence of "the" is at index 10.
The last occurrence of "the" between the start and index 8 is at index 6.
The last occurrence of "the" between index 10 and index 5 is at index 10.
*/